While the invention may find other uses, the ensuing description refers specifically to its use with blood glucose monitoring systems.
Those who have irregular blood glucose concentration levels are medically required to regularly self-monitor their blood glucose concentration level. An irregular blood glucose level can be brought on by a variety of reasons including illness such as diabetes. The purpose of monitoring the blood glucose concentration level is to determine the blood glucose concentration level and then to take coffective action, if needed, based upon whether the level is too high or too low, to bring the level back within a normal range. The failure to take corrective action can have serious implications. When blood glucose levels drop too low—a condition known as hypoglycemia—a person can become nervous, shaky and confused. That person's judgment may become impaired and that person may eventually pass out. A person can also become very ill if their blood glucose level becomes too high—a condition known as hyperglycemia.
One method of monitoring a person's blood glucose level is with a portable, hand-held blood glucose testing device. The portable nature of these devices enables the users to conveniently test their blood glucose levels wherever the user may be. The glucose testing device includes a biosensor to harvest the blood for analysis. One type of biosensor is the electrochemical biosensor. The electrochemical biosensor includes a reagent designed to react with glucose in the blood to create an oxidation current at electrodes disposed within the electrochemical biosensor which is directly proportional to the user's blood glucose concentration. Such a biosensor is described in U.S. Pat. Nos. 5,120,420, 5,660,791, 5,759,364 and 5,798,031. Another type of sensor is an optical biosensor, which incorporates a reagent designed to produce a calorimetric reaction indicative of a user's blood glucose concentration level. The calorimetric reaction is then read by a spectrometer incorporated into the testing device. Such an optical biosensor is described in U.S. Pat. No. 5,194,393.
In order to check a person's blood glucose level, a drop of blood is obtained from the person's fingertip using a lancing device, and the blood is harvested using the biosensor. The biosensor, which is inserted into a testing unit or “meter” is brought into contact with the blood drop. The biosensor draws the blood, via capillary action, inside the biosensor and the ensuing electrochemical reaction is measured by the test unit which then determines the concentration of glucose in the blood. Once the results of the test are displayed on a display of the test unit, the biosensor is discarded. Each new test requires a new biosensor.
The invention concerns an adapter which permits different types of monitoring devices to exchange signals with a processor, such as a personal computer (PC) or the like. This involves electronically differentiating between and automatically adapting to an open-collector signaling convention or an RS-232 (EIA-232) compatible signaling convention.
One existing blood glucose meter has an RS-232 (EIA-232) compatible output port with a custom connector. A redesign of this meter's electronics has been undertaken to reduce cost. However, the connector is molded into the case and a mold change is beyond the project scope. Therefore, the redesigned meter must use the same connector as the earlier meter. Component and cost savings would, however, accrue if the RS-232 (EIA-232) compatible interface were replaced by an open-collector (OC) interface; however, the existing I/O cable, used for coupling the meter to a PC, would not be compatible with this change. To simplify meter-to-computer interfacing for professionals that will be seeing both meter types (i.e., OC and RS-232 (EIA-232)), it would be advantageous to develop a single cable that would automatically work with either meter. The invention provides an electronic circuit, to be implemented in a modified cable, for accomplishing the above. If a stereo plug is wired in parallel with the plug, compatibility can be extended to other existing “open collector” output meters.
Existing cables are not compatible with both signaling conventions. The one prior interface device, “Basic Cradle™” can handle both signaling conventions, but not automatically through a shared connector. This is true in part because of the incompatible plug/connector design of some other OC type meters.
The proposed invention will handle both signaling conventions automatically through a shared plug. It identifies the signal convention by monitoring for a negative marking voltage that is unique to the RS-232 (EIA-232) compatible interface of the existing meter. It uses the detected interface type to automatically correct signal polarity and adjust the signal detection level for the serial data stream. The level-shifted and polarity-corrected data stream is then fed to another level translator to produce an RS-232 (EIA-232) compatible signal for the host computer. Like at least one existing cable, the interface is powered via signal pins of the host computer interface.